**Editor's Note: Click herefor our ranking of April's hottest selling smartphones to see how Apple's iPhone fared against the competition.**

Almost 60 million VoLTE subscriptions will be in place by the end of this year, ABI Research said today, and the success of next-gen LTE technology partly hinges on device makers such as Apple.

That’s because VoLTE, even with its adoption by operators such as AT&T and Verizon, won’t work without the right gadgets.

“There are some promising signs, though," said Marina Lu, research analyst at ABI Research. “It is anticipated that Apple will incorporate VoLTE into iPhone 6."

The iPhone 6 release date remains unknown; the industry is abuzz as Apple preps for its annual Worldwide Developers Conference slated for next week.

Meantime, ABI predicts that LTE networks will cover about 64 percent of the world population by 2019. ABIT said it expects that nearly 56 of LTE-related cellular subscriptions will be using VoLTE services by the end of 2019. The firm just released its new study, “4G Subscribers, Devices and Networks."